Marine bacteria exhibit a bipolar distribution
Woo Jun Sula,
Thomas A. Oliverb,
Hugh W. Ducklowc,
Linda A. Amaral-Zettlera,d,1, and
Mitchell L. Sogina
Author Affiliations
Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved December 19, 2012 (received for review July 25, 2012)
Abstract
Full Text
Authors & Info
Figures
SI
Metrics
Related Content
PDF
PDF + SI
Abstract
The microbial cosmopolitan dispersion hypothesis often invoked to explain distribution patterns driven by high connectivity of oceanographic water masses and widespread dispersal ability has never been rigorously tested. By using a global marine bacterial dataset and iterative matrix randomization simulation, we show that marine bacteria exhibit a significantly greater dispersal limitation than predicted by our null model using the ?everything is everywhere? tenet with no dispersal limitation scenario. Specifically, marine bacteria displayed bipolar distributions (i.e., species occurring exclusively at both poles and nowhere else) significantly less often than in the null model. Furthermore, we observed fewer taxa present in both hemispheres but more taxa present only in a single hemisphere than expected under the null model. Each of these trends diverged further from the null expectation as the compared habitats became more geographically distant but more environmentally similar. Our meta-analysis supported a latitudinal gradient in bacterial diversity with higher richness at lower latitudes, but decreased richness toward the poles. Bacteria in the tropics also demonstrated narrower latitudinal ranges at lower latitudes and relatively larger ranges in higher latitudes, conforming to the controversial macroecological pattern of the ?Rapoport rule.? Collectively, our findings suggest that bacteria follow biogeographic patterns more typical of macroscopic organisms, and that dispersal limitation, not just environmental selection, likely plays an important role. Distributions of microbes that deliver critical ecosystem services, particularly those in polar regions, may be vulnerable to the same impacts that environmental stressors, climate warming, and degradation in habitat quality are having on biodiversity in animal and plant species.
Footnotes
1To whom correspondence should be addressed. E-mail: []
Author contributions: W.J.S., L.A.A.-Z., and M.L.S. designed research; W.J.S., H.W.D., and L.A.A.-Z. performed research; W.J.S., T.A.O., and L.A.A.-Z. analyzed data; and W.J.S., T.A.O., H.W.D., L.A.A.-Z., and M.L.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The sequences reported in this paper have been deposited in the National Center for Biotechnology Information Sequence Read Archive; for the list of accession numbers, see Dataset S1.
This article contains supporting information online at
www.pnas.org/lookup/suppl/doi:10.1073/pnas.1212424110/-/DCSupplemental
